This invention relates to cleaning devices for cleaning semiconductor wafers or the like, i.e., glass or disk substrates which must be kept clean, of contaminants and dust adhered to the surfaces thereof to the same cleanliness level as semiconductor wafers.
FIG. 1 shows such a conventional cleaning device for cleaning semiconductor wafers, etc. The cleaning device of FIG. 1 comprises a cleaning vessel 1, in which a cleaned object 2 such as a semiconductor wafer is supported by a support means 3. Fine frozen particles 5 such as ice particles are generated and stored by a frozen particle supply means 4. The fine frozen particles 5 are supplied to a jet means 6 such as a jet nozzle which ejects and sprays the frozen particles 5 towards the object to be cleaned 2 supported by the support means 3. Further, an exhaust duct 7 is coupled at one end to the cleaning vessel 1, for exhausting the frozen particles which have been ejected by the jet means 6 after cleaning the surface of the object 2. In addition, an exhaust blower 8 is disposed at an intermediate portion of the exhaust duct 7 so as to suck and exhaust the air from the cleaning vessel 1 forcibly to the outside.
The above support means 3 comprises a support portion 3a for fixing and supporting the object 2, and a motor 3b for rotating the support portion 3a. On the other hand, the frozen particle supply means 4 comprises a frozen particle generating container 4a, which is supplied, from a refrigerant supply source (not shown), with refrigerant such as liquid nitrogen via a refrigerant supply pipe 4b, and whose walls are surrounded by a heat insulating material 4c; and a spray nozzle 4d, which is coupled to a supply source (not shown) for supplying the liquid, such as ultrapure water, to be frozen in the container 4a, and which sprays the liquid into the frozen particle generating container 4a to generate frozen particles 5.
Next, let us describe the method of operation of the above conventional cleaning device. First, the interior of the frozen particle generating container 4a surrounded by the heat insulating material 4c is refrigerated by means of the vaporization of the refrigerant such as liquid nitrogen therewithin. After the interior of the frozen particle generating conntainer 4a is thus sufficiently refrigerated, the liquid to be frozen, such as ultrapure water, is sprayed from the spray nozzle in the form of fine particles to form fine frozen particles 5 having particle diameters of 20 .mu.m (micrometers) to 5 mm (millimeters). The frozen particles 5 thus generated are collected in a collector net 4e spread within the frozen particle generating container 4 in the form of a reversed cone; further, they are forwarded to the jet means 6 by means of the ejector principle utilizing a jet of a carrier gas, discharged and blasted therefrom together with the carrier gas against the surface of the object to be cleaned 2, such as a semiconductor wafer fixedly secured to the support portion of the support means 3. The fine frozen particles 5 ejected from the jet means 6 collide with the surface of the object 2 to scrub off therefrom any contaminants, such as fine dust and remnants of resist, adhered thereto. Since, at this time, however, the fine frozen particles 5 are ejected by means of the jet of carrier gas, upward or turbulent flows tend to form within the cleaning vessel 1, due to the jet of carrier gas being reflected by the surface of the object 2 after colliding with it. Thus, the fine frozen particles 5, which have collided with the object 2 and thus contain the contaminants scrubbed off therefrom, or the contaminants themselves which have been scrubbed off from the object 2 by the frozen particles 5, tend to re-adhere to the object 2, due to the upward or turbulent flows of the carrier gas formed within the cleaning vessel 1, or due to the interior surface of the cleaning vessel 1. Thus, the atmosphere within the cleaning vessel 1 is forcibly exhausted by the exhaust blower 8 to the outside via the exhaust duct 7, such that the upward or turbulant flows of the carrier gas are suppressed.
The above conventional cleaning device, however, has the following disadvantage. Namely, in spite of the forced exhausting by means of the exhaust blower 8, the exhausting of the interior of the cleaning vessel 1 is insufficient; that is, although the gas in the portion near to the opening of the exhaust duct 7 to the cleaning vessel 1 is relatively well exhausted, stagnations of the gas develop near the circumferential walls of the cleaning vessel 1 which are spaced far from the opening of the exhaust duct 7 to the cleaning vessel 1. Consequently, the fine frozen particles or the carrier gas ejected from the jet means 6 cannot be sucked into the exhaust duct 7 sufficiently, and hence the upward or turbulent flows of the jet of the gas cannot be suppressed sufficiently. As a result, the frozen particles 5 to which the contaminants scrubbed off from the cleaned object 2, or the contaminants themselves which have been scrubbed off from the cleaned object 2 by the frozen particles 5, cannot be prevented with sufficient effectiveness from adhereing again to the cleaned object 2, or adhering to the interior surface of the cleaning vessel 1.
Further, if all the jet flow of the carrier gas and the frozen particles ejected from the jet means 6 are to be sucked into the exhaust duct 7 so as to prevent the upward or turbulent flows in the case of the conventional cleaning device, then, an exhaust blower 8 having a large exhaust capacity is required, which results in a large-sized device and an increased cost. On the other hand, if the exhaust capacity of the exhaust blower 8 is reduced, the above disadvantage cannot be resolved.